1. Field of the Invention
The present invention relates to a novel solid source antimony precursor, and more particularly, to Br2SbCH3 and method of synthesizing same for use in ion implantation and deposition.
2. Description of the Related Art
The reduction in critical dimensions necessary for continued gains in dynamic random access memory (DRAM) circuit density will require a number of fundamental changes from current practice, relative to the techniques and source materials employed in current manufacturing practice. As geometries of such DRAM devices decrease below 0.35 micrometer, a corresponding reduction is necessary in the size of p/n dopant layer thicknesses and in the associated dopant concentrations.
The mobility of lightweight p-type and n-type dopants is too high, even with reduced thermal budgets, to accommodate the increased stringency of future implant requirements. Thus, it will be necessary to develop dopants that can be utilized in very shallow p/n layers. This implies that traditional dopants such as boron (p-type) and phosphorus (n-type) will have to be replaced due to their high mobility in silicon (which results in a breakdown of the junction, even with reduced thermal budgets).
Dopants with significantly greater size and mass, will need to be used to improve control of ion throughput and to reduce channeling effects in the fabricated structures. A logical choice for an n-type dopant is antimony, due to its greater size and mass, that provide superior diffusion characteristics relative to traditional implant species. These properties make it possible to use lower implant energies and more advantageous geometries when depositing the shallow p/n junctions that are critical to DRAM storage density increases.
Currently solid species, such as Sb2O3 and SbF3 are used to generate ion beams for ion implantation but have been found to be problematic. For example, Sb2O3 requires high temperatures to volatize, leading to particle formation from recondensation or entrainment within the ion implanter. The addition of fluorine may cause additional diffusion of which often results in contamination of the well region and loss of threshold voltage control in the resulting devices.
Chemical vapor deposition (CVD) offers a low-cost, high throughput approach to device manufacturing. However, a lack of suitable, low temperature CVD precursors has hindered its widespread applicability. This is particularly true for Sb-based heterostructures that display important optoelectronic and electronic properties, including InSb, InGaSb, InAsSb, GaAlSb and InSbBi. Unfortunately, current Sb CVD sources require processing temperatures in excess of 460xc2x0 C. to achieve precursor decomposition and useful film growth rates. Volatile and thermally stable Sb precursors would facilitate the chemical vapor deposition of antimonide thin-films, as required for the large scale, controlled production of antimonide based lasers, detectors and microelectronic sensors.
Thus, suitable volatile antimony precursors are currently unavailable. Accordingly, the art is in need of new source compositions of antimony for ion implant and CVD applications.
The present invention relates to novel antimony compounds and method of synthesizing same. The novel antimony compounds of the invention may have the formula:
X2SbCH3
wherein each X is a halogen and independently selected from the group consisting of F, Cl, Br and I, and preferably the halogen is Br. It has been expectedly discovered that the novel antimony compounds, having only one carbon molecule, exhibit high volatility.
In another aspect, the invention relates to a method of synthesizing the antimony compounds of the invention comprising:
combining a trihalide antimony compound with trimethylantimony;
heating the trihalide antimony compound and trimethylantimony at a temperature of from 30xc2x0 C. to about 90xc2x0 C. for the a sufficient amount of time to at least melt the trihalide antimony compound and to form a X2SbCH3 product; and
purifying the X2SbCH3 to form a crystalline product.
Preferably, the trihalide antimony compound and the trimethylantimony compound are combined and heated without a solvent at a temperature from about 60xc2x0 to 75xc2x0 C.
In yet another aspect, the invention relates to a method of depositing antimony on a substrate from an antimony-containing precursor therefor, comprising using as a precursor an antimony molecule of the formula:
X2SbCH3
wherein each X is a halogen independently selected from the group consisting of F, Cl, Br and I, and preferably the halogen is Br.
In such a method, the antimony compound of the invention may be deposited by a deposition process including, but not limited to, chemical vapor deposition, assisted chemical vapor deposition (e.g., laser, light, plasma, ion, etc.), ion implantation, molecular beam epitaxy, diffusion and rapid thermal processing.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.